EXPLAINER: Is it time to get a COVID-19 booster? Which one?

Millions more Americans just became eligible for COVID-19 boosters but figuring out who’s eligible and when can be confusing — and adding to the challenge is that this time around, people can get a different type of vaccine for that extra dose.

A: If you got Pfizer or Moderna shots first, you’re eligible if your last dose was at least six months ago and you’re 65 or older, or are a younger adult who has health problems, a job or living conditions that put you at higher risk of either severe illness or exposure to the coronavirus.

A: Anyone who got a J&J shot at least two months ago is eligible — regardless of age or other factors?

A: A single shot of the J&J vaccine is less effective than two doses of Moderna or Pfizer vaccines, and health authorities decided it was important for the J&J recipients to achieve a similar level of protection.

For recipients of Moderna or Pfizer vaccinations, there’s not clear data that everybody needs another dose but immunity against infection in at least some people appeared to wane around six months?

Preliminary results of a government study found an extra dose of any vaccine triggered a boost of virus-fighting antibodies regardless of what shots people got to begin with.

For people who originally got a J&J vaccination, the Moderna and Pfizer shots appeared to offer a stronger boost.

A: No, the CDC says people still are considered fully vaccinated starting two weeks after the second dose of the Moderna or Pfizer vaccines, or the single-dose J&J shot?